Long-Term Debt And Other Long-Term Liabilities (Other Long-Term Liabilities) (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2016	Dec. 31, 2015
Debt Disclosure [Abstract]
Asset retirement obligation (ARO) liability	$ 70,043	$ 70,170	$ 70,759	$ 98,297
Capital lease obligations	18,008	18,918
Workers' compensation	15,066	15,163
Separation benefit plans	5,149	4,943
Deferred compensation plan	4,924	4,578
Gas balancing liability	3,322	3,789
Other	410	410
Other liabilities	116,922	117,971
Less current portion	15,045	14,907
Total other long-term liabilities	$ 101,877	$ 103,064

The carrying amount of a liability for an asset retirement obligation. An asset retirement obligation is a legal obligation associated with the disposal or retirement of a tangible long-lived asset that results from the acquisition, construction or development, or the normal operations of a long-lived asset, except for certain obligations of lessees.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 410
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=6392692&loc=d3e7535-110849

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Asset Retirement Obligation
-URI http://asc.fasb.org/extlink&oid=6505190

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- Definition

Amount equal to the present value (the principal) at the beginning of the lease term of minimum lease payments during the lease term (excluding that portion of the payments representing executory costs such as insurance, maintenance, and taxes to be paid by the lessor, together with any profit thereon) net of payments or other amounts applied to the principal through the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=6455398&loc=d3e45280-112737

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 03
-Paragraph 16
-Article 7

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No definition available.

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- Definition

Aggregate carrying value as of the balance sheet date of the liabilities for all deferred compensation arrangements. Represents currently earned compensation under compensation arrangements that is not actually paid until a later date.

+ References

No definition available.

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- Definition

The value of gas balancing asset or liability as of the end of the period.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 932
-SubTopic 10
-Section S99
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-URI http://asc.fasb.org/extlink&oid=50486907&loc=d3e512571-122862

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- Definition

Carrying value as of the balance sheet date of obligations incurred through that date and payable for employer-related costs not otherwise specified in the taxonomy.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03.15(a))
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-Name Accounting Standards Codification
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The aggregate carrying amount, as of the balance sheet date, of liabilities not separately disclosed in the balance sheet.

+ References

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-Name Accounting Standards Codification
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Aggregate carrying amount of current liabilities (due within one year or within the normal operating cycle if longer) not separately disclosed in the balance sheet. Includes costs that are statutory in nature, are incurred on contractual obligations, or accumulate over time and for which invoices have not yet been received or will not be rendered and of liabilities not separately disclosed.

+ References

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Aggregate carrying amount, as of the balance sheet date, of noncurrent obligations not separately disclosed in the balance sheet. Noncurrent liabilities are expected to be paid after one year (or the normal operating cycle, if longer).

+ References

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- Definition

The aggregate carrying amount, as of the balance sheets date, of obligations not otherwise itemized or categorized in the footnotes to the financial statements.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 02
-Paragraph 24
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- Definition

Carrying value as of the balance sheet date of obligations and payables pertaining to claims incurred of a workers compensation nature.

+ References

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